1. Field of Invention
The present invention relates in general to a structure of a driving circuit of a flat panel display device, and more particular, to a driving circuit of a flat panel display device operative to deliver more driving signals with less number of signal lines.
2. Related Art
The flat panel display device is a very popular display device, among which the liquid crystal display device has been widely applied to desktop personal computer, laptop computer, personal data assistant, and other portable information technique devices because of the features of light, thin, low power consumption, and non-radio pollution. The conventional monitors and television using cathode ray tubes have been gradually replaced by the flat panel display devices.
In general, the driving circuit of the liquid crystal display device uses a tape carrier package (TCP) packaged with a plurality of driver ICs to electrically connect the printed circuit board of an image processing device and a lower glass substrate of a liquid crystal display panel, so as to transmit control signal from the printed circuit board to corresponding driver ICs, followed by inputting the processed signals to each pixel of the lower glass substrate. To save the cost and to improve the exterior dimension of the product, the wiring on array (WOA) structure is generally adapted in the liquid crystal display device.
FIG. 1 shows a conventional WOA liquid crystal display device 10 including a liquid crystal display panel 12, a plurality of source TCPs 14 electrically connected to a horizontal edge of the liquid crystal display panel 12 and a source PCB 16, a plurality of gate TCPs 18 electrically connected to a vertical edge of the liquid crystal display panel 12, a plurality of source driver ICs 20 each formed on a corresponding source TCP 14, and a plurality of gate driver ICs 22 each formed on a corresponding gate TCP 18. In addition, the liquid crystal display panel 12 includes a lower substrate 24 of thin-film transistor for allocating each signal lines, an upper substrate 26 for allocating color filters and a liquid crystal layer (not shown) sandwiched between the lower and upper substrates 24 and 26. The liquid crystal display panel includes a picture display area 28 which comprises a plurality of scan lines 30 and data lines 32 perpendicularly intersecting each other to electrically connect the corresponding gate driver IC 22 and the corresponding source driver IC 20, respectively.
As shown in FIG. 1, the source TCPs 14 include a plurality of source input pads 34 and a plurality of source output pads 36 for electrically connecting the source PCB 16 to the data lines. Further, the source PCB 16 closest to the gate TCPs 18 includes a set of gate driving signal transmission line 37 for electrically connecting the WOA gate driver bus 38 on the lower substrate 24 in WOA manner. Each of the gate TCPs 18 includes a set of gate driving signal transmission line 40 and a plurality of gate output pads 42 electrically connected to the corresponding gate driver ICs 22.
As shown in FIG. 1, the signal transmitted from the source PCB 16 includes a gate driving signal and a source driving signal. The source driving signal is transmitted to the source driver IC 20 from the source PCB 16 via the source input pad 34, through which the source diving signal is further delivered to various data lines 32. On the other hand, the gate driving signal is transmitted from the source PCB 16 to the gate driving signal transmission line 37 of the source TCP 14. Being transmitted to the gate driving signal transmission line 40 of the gate TCP 18 by the WOA gate driving signal bus 38, through such step, the gate driving signal is transmitted to the scan line 30 of each gate driver IC 22. Therefore, the conventional liquid crystal display device 10 requires a gate driving signal transmission line 37 installed in the source TCP 14 to transmit the gate driving signal. Thus design, the surface area of the horizontal side of the liquid crystal display panel 12 has to be increased for installing the source TCP 14 including gate driving signal transmission line 37 and the WOA gate driving signal bus 38.
Further, to further reduce cost, the industry has developed a liquid crystal display device based on chip on glass (COG) technique. That is, the source driver IC 20 and the gate driver IC 22 installed on the lower substrate surface of the liquid crystal display panel are realized by forming a source driving transmission line in a flexible printed circuit (FPC) to electrically connect the source driver IC, so as to transmit the source driving signal. Meanwhile, the gate driving signal transmission is formed in the FPC, and a WOA gate driving signal bus formed on the horizontal and vertical sides of the liquid crystal display panel provides the electrical connection from the gate driving signal transmission to each gate driver IC. This technique, although reduces partial cost by using COG to form the source and gate driver IC on the lower substrate surface, cannot resolve the problem of increased surface area of the horizontal side of the liquid crystal display panel required for forming the signal transmission devices related to the gate driving signal.
Therefore, it is a substantial need for the industry to effectively reduce the number of signal lines for driving signal transmission, to reduce the wiring space of the substrate surface of each liquid crystal display device, and to reduce the panel area and cost.